Method for using high density compressed liquefied gases in cleaning applications

ABSTRACT

A method uses a high density compressed liquefied gas in cleaning applications in a closed recycle system to achieve effective and economical cleaning without using any high pressure generating device. The closed recycle system can include a pressure cleaning vessel provided with a plurality of nozzles for pre-cleaning, atmospheric containers for expanding compressed liquid, sound wave generators and an agitator. The system can also include a pressure recovery vessel provided at a lower portion than the pressure cleaning vessel and having a detachable drain cylinder suspended from under the pressure recovery vessel and also having a temperature regulator for receiving contaminated liquid that has been pre-cleaned from a pressure cleaning room. The pressure recovery vessel can be connected with a high density compressed liquefied gas supply cylinder through communication with vapor therein to eliminate enriched liquid with contaminants through the drain cylinder as well as removing and transferring solvent by the vapor occurred from the temperature regulator.

TECHNICAL FIELD

This invention entitled "Method for using high density compressedliquefied gases in cleaning applications" relates to a cleaning means,which can achieve high efficiency at low cost by using a series ofcleaning steps as cleaning factors, such as physical energy, chemicalforce and salvation and provides a new system for the recycle andrecirculation of cleaning solvents without any expensive high pressuregenerating equipments, such as compressors, high pressure pumps orothers.

BACKGROUND ART

Semiconductors and the like hereafter referred to as objects to becleaned are placed inside a pressurized cleaning vessel in whichsupercritical fluid is fed for cleaning of the said objects to becleaned by contacting with supercritical fluid and dissolution ofimpurities adhered to the objects. The supercritical fluid iscirculated. When eliminating the supercritical fluid in which thesecontaminatns dissolved from the pressurized cleaning vessel by asuitable means, the objects which were precisely cleaned are obtained. Atroublesome process for drying the objects required in so-called wetcleaning methods is unnecessary since the supercritical fluid iscompletely vaporized by a decompressing operation.

It is possible to reuse the supercritical fluid because suchsupercritical fluids with the above-mentioned contaminants aretransferred from the cleaning vessel into a separation tank (or arecovery tank) and then the solvent is separated from the contaminantsby mechanism stated whithin.

As shown in the FIG. 7 concerning a schematic plot of the states of thepure substance and Its supercritical state, this is the latest techniquefor cleaning semiconductor substrates by using the following twocharacteristics of the supercritical fluid in its high density fluidstate in which condition of pressure and temperature at the nearcritical region is P>P. (crirical pressure) and T>T. (criticaltemperature).

Characteristic 1: It is possible to easily obtain a great change indensity with a slight change of pressure. It is also possible to obtaina great difference or solubility because the solubility of substance isin general, proportional to the density thereof.

Characteristic 2: The density of a supercritical fluid has low viscosityand high diffusivity although it is similar to liquid. Therefore, such acharacteristic is advantageous when a 'substance moves.

The priciple shows that firstly, the low viscosity of the supercriticalfluid can easily enter into narrow pores and crevices. On the contrary,for the case of high viscosity thereof, the fluid has high solubilityfor contaminants adhered or penetrated into a substrate, especiallyorganics substances. Secondly, the above-mentioned cleaning operation isachieved with the supercritical fluid containing the contaminatingsubstance, and the contaminants can be divided between solid and liquidstates because solubility of the said contaminants is weakened bydecreasing the density thereof. Accordingly, in this invention, it ispossible to recover these components by a decompression operation in aseparation vessel.

After the contaminants are separated from the solution, the purifiedsupercritical fluid used in the pressurized cleaning vessel can bestored and recycled resulting in a closed recycle system.

Applicable gases in this invention are carbon dioxide, nitrous oxide,ethane, propane and the like. In particular, carbon dioxide is highlysuitable to handle since it is nonflammable, nontoxic and inexpensive,and has a critical temperature of 31.1° C. and a critical pressure of72.8 atmospheres.

In such a recycle system mentioned above, a general fluid tranfer methodcan be accomplished with a high pressure generator such as compressors,pumps, etc. to make and keep the supercritical state. However, suchequipment as cleaning equipments are very costly since these equipmentsneed the high ability to generate high pressure, and further thesemethods are known to generate fine particles that are detrimental to thecleaning process.

Even though it is possible to depend only upon the use of solvents forcleaning, for a case when this is not effective, it is available to useforced means, for example agitation and/or ultrasonic energy forpromoting cavitation in order to impart cleaning action. The variouscontaminants to be difficult to dissolve can be effectively dissolvedwith addition of an entrainer.

The above-mentioned characteristics of the supercritical fluid are toinclude near-critical fluids. As shown in the pressure-temperaturediagram of FIG. 7, a near-critical fluid denotes that a fluid exists inthe neighbouring region of the critical point and the fluid exists as acompressed liquid and a compressed gas. Fluids in this region andsupercritical fluids behave distinctly. What exists in the near criticalregion or the supercritical region of the neighbouring region pointabove the critical temperature is given the name of a high densityliquefied gas.

As an example, there is a simple cleaning method to reduce costdisclosed in the Japanese Patent Publication No. 7-171527 (1995), whichteaches a means as to a high density liquefied gas used as solvent inthe critical region and supercritical fluid but requires high pressuremajor equipment components.

The features in said Japanese Patent Publication are a means oftemperature control provided in a cleaning vessel and the use ofultrasonic energy for cavitation. Namely, what was described in saidPublication is only one means to improve cleaning efficiency withtemperature control using a high density liquefied gas in a cleaningvessel with cavitation produced from ultrasonic energy.

However, this method teaching in said Publication is still insufficientfor reducing cost since a pump and the like are employed as the power totransfer a high density liquefied gas in a process for removingcontaminants and recoveriing solvent in a closed recycle system.Moreover, particles and other contaminants. either as metals,inorganics, degraded seals or gaskets or as lubricants, oils or otherundesirable fluids, are introduced into the cleaning system through useof these high pressure major equipment components. Furthermore, in thismethod mentioned above, it is not sufficient to completely removecontaminants by cavitation with strong agitation for supplementingreduction of the cleaning advantage of high permeability in asupercritical state because only the partially projected contaminantsare removed. Although cleaning in this method is carried out byimmersing the objects to be cleaned in liquid which is indispensable forcavitation, contaminants in the liquid re-adhere onto the objects due tomany solid contaminants being In the liquid. Thus, such a method inprior art has an inconvenient factor because there is a re-cleaning stepas another process for achieving complete cleaning. Further, for thecase of using a high density liquefied gas including CO₂ as solventhaving the critical temperature in the vicinity of room temperature, itis hardly expected that contaminants adhered on inorganic compounds,polar substances and others having remarkable characteristics of beingdifficult to dissolve are perfectly removed even though entrainers wereadded for increasing the cleaning effect. Therefore, at the presenttime, there is great anticipation among these in the trade of how such adifficult problem can be solved simply and improved for industrialapplications.

In view of the above-mentioned contemporary circumstances that are notedto be difficult to improve, one objective in this invention is toprovide a new method using a high density liquefied gas for achievingthe cost reduction, remarkably powerful cleaning, an effective cleaningmeans for solving a difficult problem as to re-adhering and especially.a complete cleaning of contaminants consisting of inorganic compounds,polar substances, etc., even if the solvent has the critical temperaturein the vicinity of room temperature.

DISCLOSURE OF THE INVENTION

A method for cleaning in this invention is achieved by the followingmeans.

Cleaning equipment using a high density compressed liquefied gas whereina closed recycle system comprises:

a pressure cleaning vessel provided with a cleaning basket supported inspace within said pressure cleaning vessel for accomodating the objectsto be cleaned and a plurality of nozzles to emit a spray of compressedliquid directly to said objects to be cleaned, and atmospheric containerplaced over and connected to said pressure cleaning vessel, saidcleaning vessel further provided with an agitator consisting of animpeller disposed in the bottom of said cleaning vessel and sound wavegenerator directed towards said impeller and disposed in said wall ofsaid cleaning vessel;

a pressure recovery vessel equipped with means for controllingtemperature and placed under and branched from said pressure cleaningvessel for receiving the used cleaning liquid after the cleaning processand having a drain cylinder detachably suspended from under saidpressure recovery vessel;

a high density compressed liquefied gas supply cylinder equipped withmeans for controlling temperature and placed over said pressure cleaningvessel so as to provide communication with the upper portion of saidpressure recovery vessel and storage for receiving the upper vaportherefrom;

an entrainer vessel disposed and connected halfway the feed line betweensaid high density compressed liquefied gas supply cylinder and saidpressure cleaning vessel; and

said vessels for supplying and receiving the respective compressedliquid are communicating between the respective upper portions thereoffor providing communication between the upper vapor in the respectivevessels.

According to the above-mentioned means, the advantages of a high densityliquefied gas which exists In the both regions of the near-criticalregion and the supercritical region in the neibouring region of thecritical point can be practically used. As already mentioned, in thisinvention, it is greatly expected to decrease costs of operation andmaintenance, and is not necessary to use any expensive equipments, suchas a high pressure generator since solvent transfer is completelycarried out by gravity set in level differences based upon vaporpressure and under vaporized state due to low energy for transferringheat, vaporization and liquefaction.

As a further advantage, the elimination of the pressurizing componentsin the system removes a large source of contaminants and impuritiesintroduced into the system by use of such components.

Furthermore, the pressure cleaning vessel having the pressure recoveryvessel placed under from said pressure cleaning vessel for communicatingeach other immediately removes massive contaminants already cleaned byemission of a plurality of nozzles for pre-cleaning outside saidpressure cleaning vessel for preventing re-adhesion of the contaminants,and as the next step for complete cleaning, contaminants are cleaned byfurther clensing under a condition filled with solvent, which can beadvantageously isolated and evacuated so that further cleanings do notcontain contaminants from previous cleanings. For these results, thechance to re-adhere massive contaminants to the objects to be cleaned isabsolutely prevented with the described. invention. Thus, it is expectedto perfectly clean the objects to be cleaned because It is possible torepeat such a cleaning method to achieve the desired level ofcleanliness.

An advantage in this invention is that with the characteristicphenomenon of the critical region, it is possible to create bubblingthroughout all regions in said pressurized cleaning vessel when thesolvent is expanded slightly by exposure to atmospheric conditions,namely, in micro-processing manufacture, and cavitation can be furtherpromoted by agitation made by generating ultrasonic energy throughoutthe solvent.

Wherein, it is possible to Install an ultrasonic generator forprojection within this cleaning system and also possible to transferthis energy together with an agitator into every vessel, which gives alarge effect in comparison with the case of partial projection.

For the case of difficult to clean contaminants that cannot be removedwith single component high density liquefied gases, it is possible toachieve cleaning of inorganic substances and polar compounds by addingan appropriate surfactant for each of the contaminants, which is theso-called micelle phenomenon recently discovered for solvatingcontaminants. Further, the contaminants solvated as a micelle that forman effective barrier can be prevented from re-adhering, which representsan advance in cleaning.

The cleaning method in this invention is achieved with theabove-mentioned cleaning mechanism and cleaning equipment consisting ofa pressure cleaning vessel provided with a cleaning basket supported inspace within said pressure cleaning vessel for accomodating the objectsto be cleaned and a plurality of nozzles to emit a spray of compressedliquid directly to said objects to be cleaned, and atmosphericcontainers placed over and connected to said pressure cleaning vessel,said cleaning vessel further provided with an agitator consisting of animpeller and disposed in the side walls of said cleaning vessel, and apressure recovery vessel equipped with means for controlling temperatureand placed under and branched from said pressure cleaning vessel forreceiving the used cleaning liquid after the cleaning process and havinga drain cylinder detachable and suspended from under said pressurerecovery vessel.

In the cleaning process mentioned above, said atmospheric containersprovided with a means for controlling temperature cool down the feedgas, liquefy and restore into said pressure cleaning vessel through arecycle supply system, and with such a solvent cycle, it is practical topermanently perform the above-mentioned cavitation for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of the basic equipment configuration of thisinvention,

FIG. 2 shows a schematic for the multiple use of recycle system,

FIG. 3-a shows a pre-cleaning as a typical cleaning mode in a pressurecleaning vessel,

FIG. 3-b shows a main-cleaning as another typical cleaning mode wherein,and

FIG. 3-c shows a schematic of an agitation equipment.

FIGS. 4 and 5 respectively show schematics for equipments as additionalfunctions of this invention,

FIGS. 6-a and 6-b respectively show schematics for a pre-cleaning and amain-cleaning in a cleaning mechanism of this invention, and

FIG. 6-c shows a schematic for an agitating equipment.

Finally, FIG. 7 is a state diagram for a pure component showingsupercritical fluid and near critical fluid regions.

BEST MODE FOR EMBODYING THE INVENTION

Detailed explanation of this invention is given in accordance with theaccompanying figures.

As shown in FIG. 1, a pressure cleaning vessel (1) supports a cleaningbasket (2) in space directly under a plurality of nozzles (3) (foreffective cleaning) within said pressure cleaning vessel foraccomodating the objects to be cleaned. In this case, it Is desirablefor nozzles (3) to have turnable necks. A jet stream is emitted fromsaid nozzles (3) to the objects to be cleaned in said basket (4) for apre-cleaning. The emitted jet stream strikes appropriately to theobjects to be cleaned and the impact energy strips off or forces offcontaminants effectively. A solvent raw material supply cylinder (6)filled with a high density liquefied gas supplies compressed liquid (5)into said pressure cleaning vessel (1) from a high pressure tube (4) andsaid nozzles (3), and in an example in FIG. 1, a temperature controller(7) is accomodated into a box (8) provided at a higher position fromsaid pressure cleaning vessel (1) due to the level difference with saidvessel (1) for supplying and/or transferring said compressed liquid (5).(In this case, a transfer of said liquid (5) is reliably performed withvapor pressure difference set at higher temperature than said pressurecleaning vessel (1) when said temperature controller (7) is accomodatedinto said supply cylinder (6), and further such a transfer is supportedthrough a high pressure tube (9) connecting at upper portions of theboth vessels.)

Some atmospheric containers (10, . . . . . ) connected to the upperportion of said pressure cleaning vessel (1) are disposed to expandspace within said cleaning vessel (1). Consequently, with saidatmospheric. container (10s), it is possible to expand said compressedliquid (5) filling said pressure cleaning vessel (1) to create bubbling.Further, as shown in detail in FIG. 3-c, impellers (11) are disposed ata portion directly under said cleaning basket (2) and also the portionin the bottom of said cleaning vessel (1), a sound generator (12)directed towards said impellers (11) is disposed along with the wall insaid pressure cleaning vessel (1), and then a powerful agitation isperformed with the mutual operation for a forced agitation caused bythese equipments and cavitation arisen with said impellers (11) rotatingby ultrasonic energy. Through these operations, the main cleaning forthe objects to be cleaned can be performed in said filled compressedliquid (5) together with such a strong agitation. The afore-mentionedbubbling and cavitation cause sudden decompression that is effective forkilling and destroying bacteria and also bacillus.

An entrainer vessel (13) is connected at a halfway portion between saidtube and a nozzle (3). In case that there are. impurities to bedifficult to dissolve by only high density compressed liquefied gas,such impurities are sucked and added into the compressed liquid (5) inthe tube (4) due to an orifice working, because the surfactants havingcharacteristics to be useful for contaminants of lipophilic, hydrophilicand/or the both of them are dissolved in advance in said entrainervessel (13). As said surfactants can dissolve the above-mentionedimpurities with the so-called micelle phenomenon, this yields aneffective barrier and makes it difficult for particles to re-adhere.

A pressure recovery vessel (14) is equipped for receiving cleaningliquid (5') at a lower portion from a pressure cleaning vessel (1).Wherein, said liquid (5') is smoothly received with a fall of the liquidlevel, a difference in vapor pressure and a vapor-mutual connection.Said pressure recovery vessel (14) with an internal temperatureregulator (15) has a drain cylinder (16) detachably suspended from undersaid vessel (14). Therefore, as a remarkable recycle system in thisinvention, it is possible to severe the connection of said draincylinder (16) filled with contaminants and also re-connect an emptydrain cylinder (16). In this system, said pressure recovery vessel (14)has a role of the vapor space of said pressure cleaning vessel (1).Namely, for the above mentioned pre-cleaning, since contaminantsincluding massive impurities are immediately flown through the tubeswith excess cleaning liquid (5'), the liquid does not stay inside saidpressure cleaning vessel (1) (See FIG. 3-a). Consequently, with theaforementioned main-cleaning and pre-cleaning, and disconnection ofvapor-mutual connection, the compressed liquid (5) that is loaded withcontaminants is eliminated from the system, which increases the cleaningefficiency (FIG. 3-b). Finally, in this invention, the problem ofso-called re-adhesion is completely solved.

For repetitive cleaning, high cleaning efficiency is assured. Then, saidpressure cleaning vessel (1) and said pressure recovery vessel (14)prevent re-adhesion and furnish an excellent mechanism for completecleaning. Thus, for the case of cleaning numerous difficult to dissolveimpurities with single component high density liquefied gases,surfactants that have affinity to the contaminants are used to createthe so-called micelle phenomenon that improves cleaning power andprevents particles from re-adhering, and with nozzle impact energy,forces their removal along with bubbling, cavitation, super high-speedagitation and chemical complexes, an advance in cleaning efficiency isrealized.

The vapor space of said pressure cleaning vessel (1) is connected with avapor path tube (17). The vapor of said pressure recovery vessel (14) isconnected through a tube (19) with the upper portion of a high densitycompressed liquefied gas supply cylinder (18) as a means for storagewithin a closed recycle system placed over the pressure cleaning vessel(1), and then with a temperature controlling regulator (15) in saidpressure recovery vessel (14), the vaporized solvent is transported tosaid cylinder (18) by the vapor-pressurized difference. On the otherhand, the vapor density is low and the salvation force is small so thelarge specific gravity of the contaminants as well as entrainers aredeposited and concentrated in the liquid at the bottom. The concentratedpart falls with gravity to a drain cylinder (16), where contaminants canbe isolated from the system and separated. In brief, the essence of anachievement is that said pressure recovery vessel (14) and said highdensity compressed liquefied gas supply cylinder (18) provide separationand recovery, contaminant removal, solvent recovery and transportwithout any specialized high pressure generators. Final result is thatlow capital and operating cost can be easily realized with thisinvention.

With an internal temperature controlling regulator (20) for saidcylinder (18), the above-mentioned vaporized solvent can be cooled andliquefied. A tube (21) connected at the lower portion of said cylinder(18) is connected another tube (4) to connect with a nozzle (3) of thepressure cleaning vessel (1). A communicating tube (22) for all vapor isprovided in order to complete fluid transportation arisen by liquidlevel drop. In this case, such a drop is completed by a temperaturedifference occured by heating with said temperature controllingregulator (20). Thus, a new and original recycle system for a completecleaning in which solvent circulation is completely achieved by an onlymeans for controlling temperature and without any expensive highpressure generators can be supplied. The elimination of high pressuregenerators also reduces a source of contamination critical tosemiconductor applications.

FIG. 2 shows an example in which the above-mentioned recycle system (--apressure recovery vessel (14)--a high density compressed liquefied gassupply cylinder (18)--) is provided for a multiple use. which canexceedingly increase the function and potentiality of said pressurecleaning vessel (1). Both systems can send liquid by changing three-wayvalves (23) and (24), which allows vapor to be sent from a valve (25)through the junction at a valve (26). The under-mentioned is anexplanation with use of this method for an actual operation with CO₂ tobe a solvent.

All of the equipment in this invention are arranged inside a room (28)with air conditioning control equipment (27) that guarantees atemperature of 20° C., which is comfortable for people who are workingin manufacturing. A cylinder (6) is controlled at 30° C. with atemperature control regulator (7). For the case of the cleaning objectswith surfactants and the like, the temperature of the compressed liquid(5) in said pressure cleaning vessel (1) is decreased to about 20° C. Insaid pressure recovery vessel (14), the temperature becomes 30° C. dueto said temperature control regulator (15). For this, the upper part ofthe liquid is mostly vaporized. Single overall vaporization time tor4-U.S. gallons requires about 40 minutes however, being that this is adual system, the time can be reduced to 20 minutes. The high densitycompressed liquefied gas supply cylinder (18) is filled with compressedliquid (5) through cooling at 0° C. with said temperature controlregulator (20).

On the other hand, when loading the objects to be cleaned into saidpressure cleaning vessel (1), it takes about 10 minutes until cleaningcan commence, however with the dual system, the waiting time for thenext cleaning is negligible, which allows the realization of highoperation efficiency.

Next, as a matter of course, the advanced cleaning features in FIGS. 4to 6 will be explained as follows.

Objects to be cleaned are placed into a cleaning basket (102) andsupported In said pressure cleaning vessel (101) directly under multiple(necessary for more effective cleaning) nozzles (103). In this case, itis desirable for the nozzles (103) to be adjustable. A jet stream isemitted from said nozzles (103) that strikes and pre-cleans the objectsto be cleaned inside of said cleaning basket (102). The impact energyincurred by the emitted jet stream is effective to force off or removecontaminants.

Further, as shown in the details of FIG. 6-c, impellers (105) aredisposed at a portion directly under said cleaning basket (102) and alsoa portion in the bottom of a vessel (101), a sound generator (106)directed towards said impellers (105) is disposed along with the wall insaid vessel (101), and then powerful agitation is performed with themutual operation for a forced agitation caused by these equipments andcavitation arisen with said impellers (105) rotating by ultrasonicenergy. The above-mentioned cavitation produced by sudden decompressionis effective for destroying and killing bacteria as well as bacillus. Apressure recovery vessel (108) is provided for accepting cleaning liquid(107') through a tube (122) placed at lower portion from said pressurecleaning vessel (101). Such an acceptance of cleaning liquid is smoothlyperformed due to the differences of level and vapor pressure(--temperature control regulator (109) for establishing a temperaturegradient is described later--) Said vessel (108) with an internaltemperature control regulator (109) has a detachable drain cylinder(110) disposed at the bottom of said vessel (108).

Said pressure recovery vessel (108) has an important role as a dividedroom for said pressure cleaning vessel (101). Namely, when performingthe above mentioned pre-cleaning for removing contaminants (includingthe massive impurities) soaked in the cleaning liquid (107'), saidliquid does not stay in said pressure cleaning vessel (101) since saidliquid is immediately received (FIG. 6-a). Therefore, in theafore-mentioned main-cleaning which is performed with the filledcompressed liquid (107) in said pressure cleaning vessel (101) afterseverance of the above-mentioned connection, a complete cleaning effectcan be realized because the major contaminants have been already removedin the pre-cleaning (FIG. 6-b). Thus, a problem as to re-adhesion whichwas very important is entirely solved. In this invention, all ofimpurities can be removed rapidly by collecting them in a drain cylinder(110), which can be taken off from the system and emptied repeatedly sothat it is possible to realize the infinite emission with this system.

Furthermore, in the above narrative of the actual cleaning, the entiresolvent boils and there is a cavitation action. An atmospheric container(112) for vapor expansion having a temperature controlling regulator(111) as a means is connected to the upper portion of the pressurecleaning vessel (101) through a vapor path tube (113) and a liquidsupply tube (114). and cavitation with expansion is performed for theentire liquid by connection with said vapor path tube (113) whilecleaning for a main-cleaning with compressed liquid (107), which isdifferent from a case of using ultrasonic projection. This cavitation iscontinously repeated by acceration for cooling the liquid with saidtemperature controlling regulator (111) and connection with a liquidphase supply tube (114). Finally, such a turbulent flow as an idealwhich has excellent salvation can be realized.

For the case that there are Impurities difficult to dissolve by only ahigh density compressed liquefied gas, such impurities can be dissolvedby solvent with the surfactants having characteristics for lipophilic,hydrophilic and/or both or them that were added in advance (--so-calledmicelle phenomenon--), which creates an effective barrier againstparticle re-adhesion.

FIGS. 4 and 5 show various arrangements, and FIG. 4 shows methods forsolution transport that without exception form a closed recycle systemwith the high pressure equipment including the above mentioned cleaningmechanisms.

A solvent raw material cylinder (116) filled with a high densitycompressed liquefied gas supplies compressed liquid (107) to a pressurecleaning vessel (101) from a nozzle (103) through a high pressure tube(115), and a temperature control regulator (117) is accomodated into abox (118) placed higher than said pressure cleaning vessel (101) inorder to send said compressed liquid (107) by level difference fall[namely, temperature control regulator (117) establishes a highertemperature for the cylinder (116) and the vapor pressure differencecauses reliable fluid transfer to the above pressure cleaning vessel(101) along with the connection of the vapor spaces through the tube(119) for the vapor]. Said high pressure tube (115) joins said liquidphase supply tube (114) at the three way valve (130) and a cylinder(116) or otherwise an atmospheric container (112: a low pressure space)is connected to allow liquid to be fed. An entrainer vessel (120) isconnected to said high pressure tube (115) just before the nozzles(103). For said entrainer vessel (120), for the case of difficult toclean contaminants that can not be removed with single component of highdensity compressed liquefied gases, a lipophilic or hydrophilicsubstance or possible a surfactant (112) that has affinity for thecontaminant is absorbed in the compressed liquid (107) by additionthrough an orifice in the connection to the tube (115). There is a tube(123) for vapor connection between the pressure cleaning vessel (101)and the pressure recovery vessel (108), which is identical to theabove-mentioned vapor path. The vapor phase in the pressure recoveryvessel (108) is connected through a tube (125) with the upper portion ofa high density compressed liquefied gas supply cylinder (124) placed inhigher space from the pressure cleaning vessel (101) as a storage meansin a recycle system, the vaporized solvent with the temperaturecontrolling regulator (109) in the pressure recovery vessel (108) istransfer to said high density compressed liquefied gas supply cylinder(124) by means of the vapor pressure difference. On the other hand,contaminated gravity substances and/or entrainers are deposited andconcentrated in the lower liquid phase since the vapor phase density ofsuch substances is low and also its solvating power is weak. Theseconcentrated substances are fed to the below drain cylinder (110) to beremoved and are separated from the system.

Therefore, a separation and recovery mechanism consisting of saidpressure recovery vessel (108) and said high density compressedliquefied supply cylinder (124) can realize contaminant removal andtransport of recovered solvent without the need for specializedpressurizing equipment.

A cylinder (124) having an internal temperature controlling regulator(126) cools and liquefies the above-mentioned vaporized solvent. A tube(127) connected with the lower part of a cylinder (124) is connectedwith a tube (115) in order to further connect to nozzles (103) in thepressure cleaning vessel (101). For completing such a transportation offluid occurred by level difference, a vapor phase path tube (128) isarranged and connected. Furthermore, under these circumstances, settingsaid temperature control regulator (126) to heat allows the transfer tobe complete. Wherein, a practical system for solvent recycle andrecirculation is supplied by using only a temperature control method.

Then, not only excellent cleaning along with a closed recycle system isprovided but also, through solvent transport of raw materials throughlevel differences, vapor pressure differences with appropriate vaporphase connections, specialized equipment is unnecessary which allows fora considerable reduction in capital costs and expenses.

FIG. 5 shows solvent transport from a cylinder (116) to said pressurecleaning vessel (101) for the case of using a high pressure generator inthe closed recycle system mentioned above, in which the same marks inFIG. 4 are used. In this case, it is not necessary for the cylinder(116) to be arranged at the upper portion from said pressure cleaningvessel (101) since a compressor (129) for deliverying the fluid isprovided. A connection between both vapor phases is omitted. Similarly,a coonection between the pressure cleaning vessel (101) and the pressurerecovery vessel (108) is omitted. A tube (127) connected to the lowerpart of a cylinder (124) is connected just before said pressurizing pump(129) placed halfway said high pressure feed tube (115) and further, theinternal vapor phase connection between the cylinder (124) and saidpressure cleaning vessel (101) are omitted.

In this Figure, a mark 104 shows a filter arranged at the supply side ofthe cylinder (124). Consequently, a new cleaning mechanism consisting ofa pressure cleaning vessel, an atmospheric container (an atmosphericpressure space), a pressure recovery vessel, a high density compressedliquefied gas supply cylinder, etc. and a separation and recoverymechanism actually realize a method for completing solvent recovery withpowerful cleaning and an effective renewal of contaminated substanceswithout a high pressure generator, which provides an economical and mosteffective cleaning system.

Industrial Utilization

In a cleaning method using a high density compressed liquefied gas andhaving super cleaning power with reference to this invention mentionedabove, it is possible to completely perform at levels of particle,sub-micron, super micron, etc. for precisely cleaning contaminantsadhered to semiconductor and the like that have not been perfectlycleaned with the current cleaning method.

In contemporary cleaning methods for general industries, for example,for applications in the metal manufacturing field, it takes aroundtwenty (20) to forty (40) minutes for cleaning because of necessarymultiple batch processes as various steps, such as preprocess cleaning,primary cleaning, main-cleaning, final cleaning, drying processes andothers before and after manufacturing the metal components. However,with the new cleaning method of this invention, the above-mentionedprocesses for cleaning metals can be completely finished within aroundtwo (2) to five (5) minutes since this cleaning method can realize onebatch process for such various steps, which consolidates cleaningprocesses and allows substantial cost-savings. The most remarkablefeature in this invention is applicability of cleaning not only metalsbut also for fibrous materials and furthermore, this method canpractically realize a non-polluting cleaning instead of currentdry-cleaning.

Explanation of Marks:

(1) A pressure cleaning vessel

(2) A cleaning basket

(3) Nozzles

(4) A high pressure tube

(5) Compressed liquid

(5') Cleaning liquid

(6) A solvent raw material supply cylinder

(7) A temperature control regulator

(8) A box

(9) A high pressure tube

(10) Atmospheric containers (Atmospheric pressure space)

(11) Impellers

(12) A sound generator

(13) An entrainer vessel

(14) A pressure recovery vessel

(15) A temperature control regulator

(16) A drain cylinder

(17) A vapor path tube

(18) A high density compressed liquefied gas supply cylinder

(19) A tube

(20) A temperature control regulator

(21) A tube

(22) A communicating tube

(23) A three-way valve

(24) A three-way valve

(25) A valve

(26) A valve

(27) An air conditioning control equipment

(28) A room

(101) A pressure cleaning vessel

(102) A cleaning basket

(103) Nozzles

(105) Impellers

(106) A sound generator

(107) Compressed liquid

(107') Cleaning liquid

(108) A pressure recovery vessel

(109) A temperature control regulator

(110) A drain cylinder

(111) A temperature control regulator

(112) Atmospheric containers (Atmospheric pressure space)

(113) A vapor path tube

(114) A liquid supply tube

(115) A high pressure tube

(116) A solvent raw material cylinder

(117) A temperature control regulator

(118) A box

(119) A tube

(120) An entrainer vessel

(122) A tube

(123) A tube

(124) A high density compressed liquefied gas supply cylinder

(125) A tube

(126) A temperature control regulator

(127) A tube

(128) A vapor phase path tube

(129) A high pressure pump

What is claimed:
 1. In a closed recycle system wherein objects to becleaned in a pressure cleaning vessel are contacted by a high densitycompressed liquefied gas at its near-critical point state as cleaningsolvent is injected from outside said pressure cleaning vessel,contaminants adhered to the objects to be cleaned are dissolved in thehigh density compressed liquefied gas, subsequent to which saidliquefied gas containing said contaminants is then transferred to arecovery tank or a separation vessel and decompressed to reduce thedensity of said liquefied gas so that the contaminants precipitate forseparation, and further the cleaning solvent with the contaminants orimpurities removed is reclaimed as a high density compressed liquefiedgas and stored for reuse;a method for cleaning and recirculatingsolvent, wherein a high density compressed liquefied gas existing innear-critical and supercritical state is employed as a solvent, theentire transfer of said solvent is achieved without requiring use of anyhigh pressure generating device by feeding under pressure resulting froma vapor pressure difference between vaporization and liquefactionwherein for said high density compressed liquefied gas the closer to itscritical point, the smaller the energy required for vaporization byheating or liquefaction by cooling, and by gravity settling at a setdifference in level backed up by the vapor pressure difference, while inthe pressure cleaning vessel, the high density compressed liquefied gasis sprayed to the objects to be cleaned for pre-cleaning massivecontaminants so that the contaminants can be immediately removed outsidethe pressure cleaning vessel thereby preventing re-adhesion of thecontaminants, and perfect cleaning for a variety of objects to becleaned is is achieved by forced agitation derived from ultrasonicenergy, cavitation affecting the entire solvent by its expansion, andformation of micelles.
 2. Cleaning equipment using a high densitycompressed liquefied gas wherein a closed recycle system comprises:apressure cleaning vessel (1) provided with a cleaning basket (2)supported in space within said pressure cleaning vessel for accomodatingthe objects to be cleaned and a plurality of nozzles (3) to emit a sprayof compressed liquid (5) directly to said objects to be cleaned, andatmospheric containers (10) placed over and connected to said pressurecleaning vessel, said cleaning vessel further provided with an agitatorconsisting of an impeller (11) disposed in the bottom of said cleaningvessel and sound wave generators (12) directed towards said impeller anddisposed In the side walls of said cleaning vessel; a pressure recoveryvessel (14) equipped with means for controlling temperature and placedunder and branched from said pressure cleaning vessel (1) for receivingthe used cleaning liquid after the cleaning process and having a draincylinder (16) detachably suspended from under said pressure recoveryvessel; a high density compressed liquefied gas supply cylinder (18)equipped with means for controlling temperature and placed over saidpressure cleaning vessel (1) so as to provide communication with theupper portion of said pressure recovery vessel (14) and storage forreceiving the upper vapor therefrom; an entrainer vessel (13) disposedand connected halfway the feed line between said high density compressedliquefied gas supply cylinder (18) and said pressure cleaning vessel(1); and said vessels for supplying and receiving the respectivecompressed liquid are communicating between the respective upperportions thereof for providing communication between the upper vapor inthe respective vessels.
 3. A cleaning equipment according to claim 2employing a high density compressed liquefied gas wherein said pressurecleaning vessel is provided with a plurality of exchangeable recyclesystems, each of said systems comprises a pressure recovery vessel and ahigh density compressed liquefied gas supply cylinder.
 4. A cleaningequipment according to claim 2 employing a high density compressedliquefied gas wherein a solvent raw material cylinder (6) is placed oversaid pressure cleaning vessel (1) together with means for controllingtemperature, said solvent raw material cylinder and pressure cleaningvessel are communicating between the respective upper portions thereoffor providing communication between the upper vapor in the respectivevessels.
 5. A method for operating cleaning equipment employing highdensity compressed liquefied gases according to claim 2 wherein, incases involving impurities which are difficult to be dissolved orcleaned in a single high density compressed liquefied gas, contaminantsare cleaned and prevented from re-adhesion by adding hydrophilic,lipophilic surfactant or surfactant having affinity to both hydrophilicand lipophilic solvent to the solvent through an entrainer vessel tocreate so-called micelle phenomenon which improves cleaning power andfunctions to prevent re-adhesion of contaminants, and these improvementsare combined with forced removal by the impact energy of the Jet streamfrom the nozzles, cavitation created by bubbling, agitation utilizingultrasonic wave, thereby purposefully redoubling said improvement.
 6. Acleaning mechanism having a function for preventing re-adhesion ofcontaminants which comprises:a pressure cleaning vessel (1) providedwith a cleaning basket (2) supported in space within said pressurecleaning vessel for accomodating the objects to be cleaned, a pluralityof nozzles (3) to emit a spray of compressed liquid (5) directly to saidobjects to be cleaned, and atmospheric containers (10) placed over andconnected to said pressure cleaning vessel, said cleaning vessel furtherprovided with an agitator consisting of an impeller (11) disposed in thebottom of said celeaning vessel and sound wave generators (12) directedtowards said impeller and disposed in the side walls of said cleaningvessel; a pressure recovery vessel (14) equipped with means forcontrolling temperature and subordinated under and branched from saidpressure cleaning vessel (1) for receiving the used cleaning liquidafter the cleaning process together with a drain cylinder (16)detachably suspended from under said pressure recovery vessel.
 7. In aclosed recycling system wherein objects to be cleaned accommodated in apressure cleaning vessel are contacted by supercritical fluid injectedfrom outside the vessel through means for providing a supercriticalstate, aqueous and organic contaminants adhered to the objects to becleaned are dissolved and transferred into said supercritical fluid,which supercritical fluid containing said contaminants is thentransferred to a separation tank and decompressed to reduce the densityof the supercritical fluid so that these contaminants precipitate forremoval, and further the supercritical fluid purified with thesecontaminants removed is stored with its density recovered for reuse;amethod for cleaning and recirculating solvent, wherein a high densitycompressed liquefied gas existing in both regions of near-critical andsupercritical state is employed as a solvent, the entire transfer ofsaid solvent is achieved without requiring use of any high pressuregenerating device by feeding under pressure resulting from a vaporpressure difference between vaporization and liquefaction wherein forsaid high density compressed liquefied gas the closer to its criticalpoint, the smaller the energy required for vaporization by heating orliquefaction by cooling, and by gravity setting at a set difference inlevel backed up by the vapor pressure difference, while in the pressurecleaning vessel, the high density compressed liquefied gas is sprayed tothe objects to be cleaned for pre-cleaning massive contaminants so thatthe contaminants can be immediately removed outside the pressurecleaning vessel thereby preventing re-adhesion of the contaminants, andperfect cleaning is achieved by forced agitation and cavitationaffecting the entire solvent by its expansion, which cavitation issecured and continued through recycling of the solvent.
 8. Cleaningmechanism in a supercritical fluid cleaning equipment, said mechanismcomprising:a pressure cleaning vessel (101) provided with a cleaningbasket (102) supported in a space within said pressure cleaning vesselfor accomodating the objects to be cleaned and a plurality of nozzles(103) to emit a spray of compressed liquid directly to said objects tobe cleaned, said cleaning vessel further provided with an agitatorconsisting of an impeller (105) disposed in the bottom of said cleaningvessel and sound wave generators (106) directed towards said impellerand disposed in the side walls of said cleaning vessel; a pressurerecovery vessel (108) equipped with means for controlling temperatureand placed under and branched from said pressure cleaning vessel (101)for receiving the used cleaning liquid after the cleaning process andhaving a drain cylinder (110) detachably suspended from under saidpressure recovery vessel; and a low pressure expansion vessel (112)equipped with means for controlling temperature and placed over saidpressure cleaning vessel (101), said expansion vessel providingvapor-phase communication with as well as a recycled supply of liquidphase to the pressure cleaning vessel.
 9. A supercritical fluid cleaningequipment wherein a closed recycle system comprises:a cleaning mechanismaccording to claim 8; a high density compressed liquefied gas supplycylinder (124) equipped with means for controlling temperature andplaced over said pressure cleaning vessel (101) so as to providecommunication with the upper portion of said pressure recovery vessel(108) and storage for receiving the upper vapor therefrom; an entrainervessel (120) connected halfway the liquid feed line between said highdensity compressed liquefied gas supply cylinder (124) and said pressurecleaning vessel (101); and said pressure cleaning vessel (101) andpressure recovery vessel (102), said high density liquefied gas cylinder(124) and pressure cleaning vessel (101) are commnunicating between therespective upper portions thereof for providing communication betweenthe upper vapor in the respective vessels, a solvent raw materialcylinder (116) is placed over said pressure cleaning vessel (101) andprovided with means for controlling temperature, and establishingcommunication with the pressure cleaning vessel for communicationbetween the respective upper portions for providing communicaitonbetween the upper vapor in the respective vessels.
 10. A supercriticalfluid cleaning equipment wherein a closed recycle system comprises:acleaning mechanism according to claim 8; a high density compressedliquefied gas supply cylinder (124) equipped with means for controllingtemperature and placed over said pressure cleaning vessel (101) so as toprovide communication with the upper portion of said pressure recoveryvessel (108) and storage for receiving the upper vapor therefrom; and anentrainer vessel (120) connected halfway the liquid feed line betweensaid high density compressed liquefied gas supply cylinder (124) andsaid pressure cleaning vessel (101); and the solvent is pumped through ahigh pressure pump (129) from said solvent raw material cylinder (116)to the pressure cleaning vessel (101).
 11. A method for operating acleaning mechanism according to claim 8 wherein, in cases involvingimpurities which are difficult to be dissolved or cleaned in a singlehigh density compressed liquefied gas, contaminants are cleaned andprevented from re-adhesion by adding hydrophilic, lipophilic surfactantor surfactant having affinity to both hydrophilic and lipophilic solventto the solvent through an entrainer vessel to create so-called micellephenomenon which improves cleaning power and function of preventingre-adhesion of contaminants.